src/util/build_id.c

   1 /*
   2  * Copyright © 2016 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #ifdef HAVE_DL_ITERATE_PHDR
  25 #include <dlfcn.h>
  26 #include <link.h>
  27 #include <stddef.h>
  28 #include <string.h>
  29
  30 #include "build_id.h"
  31
  32 #ifndef NT_GNU_BUILD_ID
  33 #define NT_GNU_BUILD_ID 3
  34 #endif
  35
  36 #ifndef ElfW
  37 #define ElfW(type) Elf_##type
  38 #endif
  39
  40 #define ALIGN(val, align)      (((val) + (align) - 1) & ~((align) - 1))
  41
  42 struct build_id_note {
  43    ElfW(Nhdr) nhdr;
  44
  45    char name[4]; /* Note name for build-id is "GNU\0" */
  46    uint8_t build_id[0];
  47 };
  48
  49 struct callback_data {
  50    /* Base address of shared object, taken from Dl_info::dli_fbase */
  51    const void *dli_fbase;
  52
  53    struct build_id_note *note;
  54 };
  55
  56 static int
  57 build_id_find_nhdr_callback(struct dl_phdr_info *info, size_t size, void *data_)
  58 {
  59    struct callback_data *data = data_;
  60
  61    /* Calculate address where shared object is mapped into the process space.
  62     * (Using the base address and the virtual address of the first LOAD segment)
  63     */
  64    void *map_start = NULL;
  65    for (unsigned i = 0; i < info->dlpi_phnum; i++) {
  66       if (info->dlpi_phdr[i].p_type == PT_LOAD) {
  67          map_start = (void *)(info->dlpi_addr + info->dlpi_phdr[i].p_vaddr);
  68          break;
  69       }
  70    }
  71
  72    if (map_start != data->dli_fbase)
  73       return 0;
  74
  75    for (unsigned i = 0; i < info->dlpi_phnum; i++) {
  76       if (info->dlpi_phdr[i].p_type != PT_NOTE)
  77          continue;
  78
  79       struct build_id_note *note = (void *)(info->dlpi_addr +
  80                                             info->dlpi_phdr[i].p_vaddr);
  81       ptrdiff_t len = info->dlpi_phdr[i].p_filesz;
  82
  83       while (len >= sizeof(struct build_id_note)) {
  84          if (note->nhdr.n_type == NT_GNU_BUILD_ID &&
  85             note->nhdr.n_descsz != 0 &&
  86             note->nhdr.n_namesz == 4 &&
  87             memcmp(note->name, "GNU", 4) == 0) {
  88             data->note = note;
  89             return 1;
  90          }
  91
  92          size_t offset = sizeof(ElfW(Nhdr)) +
  93                          ALIGN(note->nhdr.n_namesz, 4) +
  94                          ALIGN(note->nhdr.n_descsz, 4);
  95          note = (struct build_id_note *)((char *)note + offset);
  96          len -= offset;
  97       }
  98    }
  99
 100    return 0;
 101 }
 102
 103 const struct build_id_note *
 104 build_id_find_nhdr_for_addr(const void *addr)
 105 {
 106    Dl_info info;
 107
 108    if (!dladdr(addr, &info))
 109       return NULL;
 110
 111    if (!info.dli_fbase)
 112       return NULL;
 113
 114    struct callback_data data = {
 115       .dli_fbase = info.dli_fbase,
 116       .note = NULL,
 117    };
 118
 119    if (!dl_iterate_phdr(build_id_find_nhdr_callback, &data))
 120       return NULL;
 121
 122    return data.note;
 123 }
 124
 125 unsigned
 126 build_id_length(const struct build_id_note *note)
 127 {
 128    return note->nhdr.n_descsz;
 129 }
 130
 131 const uint8_t *
 132 build_id_data(const struct build_id_note *note)
 133 {
 134    return note->build_id;
 135 }
 136
 137 #endif